Physiology Flashcards
(42 cards)
0
Q
Principles of endocrine control of metabolism
A
- all pathophysiologic events are influenced by endocrine system
- all large physiologic events are mediated by multiple hormones acting together
- many known hormones
1
Q
Definition of a hormone
A
Regulatory molecules secreted by endocrine glands or special cells in the body
- act locally or transported to a target tissue
- collectively influence growth and reproduction, reproductive function and homeostasis
2
Q
Three major classes of hormones
A
- protein and peptide (insulin)
- steroid (cholesterol derived)
- tyrosine derivatives (thyroxine and epinephrine)
3
Q
Where do amine and peptide hormones bind?
A
To cell membranes
4
Q
How are peptide hormones synthesised and activated?
A
- synthesised as pro hormones
- cleaved by enzymes or amino acid sequences removed
5
Q
How do amine and peptide hormones act?
A
- rely on secondary messengers (intracellular compounds that increase in conc during amplification)
6
Q
How do secondary messengers amplify signal?
A
- hormone binds to membrane receptor
- activates adenyl cyclase (membrane-bound enzyme)
- causes intracellular ATP to convert to cAMP
- cAMP is secondary messenger and may activate protein kinases
7
Q
4 possible actions of secondary messengers
A
- cAMP
- cGMP
- calcium ions
- phosphatidylionsitol cleaved by phospholipase C to form IP3 (interacts with receptors at ER to release Ca)
8
Q
What does magnitude of hormone effect depend on?
A
- hormone concentration
- number of receptors on cell
- affinity of receptor for the hormone
- up and down reg
- saturation
- blocking with other hormone like chemicals
9
Q
Definition of Kd
A
Concentration of hormone required to occupy 50% of the receptors
10
Q
Action of steroid hormones
A
- exert effects on nucleus
- bind to and transported on cytosolic receptors
- hormone-receptor complex binds to DNA at special hormone receptor regions
- cause transcription if mRNA and coding for specific proteins
11
Q
What are the steps following receptor binding of steroid hormones?
A
- receptor activation (becomes competent to bind DNA)
- activated receptors bind to hormone response elements (short specific sequences of DNA located in promoters of hormone responsive genes)
- transcription from genes to which the receptor is bound is affected
12
Q
Definition of homeostats
A
Negative feedback controllers necessary for the maintenance of life
13
Q
Definition of gain
A
How quickly the system returns to baseline following a change
14
Q
How is infinite gain achieved?
A
By having multiple opposing but inter-dependent controllers
15
Q
When are max insulin levels found?
A
1 hour after meal
16
Q
Stimuli for glucagon release
A
- hypoglycemia
- norepinephrine and epinephrine
- amino acids
17
Q
Stimuli for insulin release
A
- hyperglycemia
- amino acids
- secretin and gastrin
- parasympathetic stimulation
18
Q
3 pancreatic islet cell types
A
- beta (insulin)
- alpha (glucagon)
- delta (somatostatin)
19
Q
Role of somatostatin
A
Inhibition of insulin and glucagon
20
Q
Describe mechanism of insulin secretion
A
- glucose signaling to insulin secretion is initiated by glucose uptake by GLUT2
- phosphorylation of glucose by glucokinase (rate limiting)
- activation of mitochondrial metabolism by pyruvate leads to prod of ATP
- ATP- dependent K channels close in response to increase ATP
- resulting membrane depolarisation opens Ca channels
- increase in cytosolic Ca induces insulin granule exocytosis and release into blood
21
Q
Hepatic and renal gluconeogenesis
A
Approximately equally productive and together give body about 100 grams of glucose per day
22
Q
Effects of cortisol
A
- maintaining adequate rates of liver gluconeogenesis during fasting (synthesis of gluconeogenic enzymes and stimulates release of substrates)
- responsible for adequate glycogen storage in liver
- catecholamine-stimulated lipolysis in adipose
- stimulate mobilization of amino acids from skeletal muscle and skin
- anti-inflam effect
23
Q
What mediates growth hormone action?
A
Somatomedins (produced by the liver)
24
Effects of growth hormone
- decreases muscle glucose uptake and increases lipolysis (anti-insulin)
- enhances amino acid uptake
25
Results of adult hypo secretion f GH
- insulin sensitivity
- hypoglycemia
- decreased muscle strength
- cutaneous atrophy
- loss of bone density
26
Action of insulin on adipose stores
- reduces circulating FFA
- enhances lipogenesis
- increases PDH, acetyl-CoA and glycerol phosphate
- inhibits activity of hormone sensitive lipase
27
Action of E,NE, glucagon, ACTH, cortisol, TSH and GH on adipose stores
- activate hormone sensitive lipase (mobilize fat store)
- GH effects on lipolysis are slow and dependent on protein synthesis
- catecholamine a stimulate lipolysis at physiological conc
28
Hormones that control protein metabolism
- GH
- insulin
- glucocorticoids
- testosterone
- thyroxine
29
How much exercise should adults do?
At least 150 mins on moderate intensity aerobic physical activity per week
30
Levels of adaptation
- molecular and cellular
- neural
- endocrine
- vascular
- metabolite and substrate
- energy substrate expenditure
31
How does exercise maintain or increase myocardial oxygen supply?
- decrease progression of coronary atherosclerosis
- improve lipoprotein profile
- improve insulin sensitivity
- decrease platelet aggregation and increase fibronolysis
- decrease adiposity
- increase coronary blood flow
- increased epicardial artery diameter
32
How does exercise decrease myocardial work and oxygen demand?
- decreases HR
- decreases arterial pressure at rest and during exercise
- increases stroke vol
- increases intrinsic myocardial contractility
33
How does exercise increase the electrical stability of the myocardium?
- decreases regional ischemia
- decreases conc of catecholamines in myocardium
- increases ventricular fibrillation threshold
34
How does chronic exercise reduce BP?
- altered responsiveness to vasoactive stimuli
- decrease intima-media thickness
- increase lumen diameter
- greater local vasodilator effect
- decreased renal sympathetic outflow
- decreased vascular responsiveness to a-adrenergic stim
- increased production of NO
35
How does exercise help in diabetes management?
- increases insulin-mediated glucose uptake for few hours after
- localized to exercised muscle (restoration of endogenous CHO stores in muscle)
36
How exercise improves insulin sensitivity
- increased insulin-mediated glucose disposal
- increased glut-4 expression in skeletal muscle
- increase in insulin receptor mRNA
- Increase IRS1
- increase in mitochondrial biogenesis
37
How exercise prevents Ca colon
- shortened fecal transit time (decrease contact between carcinogens and cells)
- favorable effects of insulin, prostaglandin and bile acid may influence growth and prolif of colonic cells
- modulation of oxidative DNA damage
38
Exercise and prevention of breast cancer
- physical activity modulates endogenous sex hormones
| - lower prevalence of obesity (independent risk factor)
39
Possible interventions
- comprehensive school-based interventions
- policies and systems that promote active transport
- urban design that promotes physical activity
- integration into primary health care
40
Mechanisms of benefit of exercise for chronic disease
- specific and general cardiovascular effects
- endothelial function
- insulin sensitivity
- increased mitochondrial biogenesis
- attenuation of muscle wasting in COPD
41
Hypotheses for obesity
- fatty acid hypothesis
- portal hypothesis
- metabolic flexibility hypothesis
- endocrine hypothesis
- HPA hypothesis
- neural hypothesis
- inflammatory hypothesis
- vasocrine overflow hypothesis
- low birth weight hypothesis
